The venom of Conus striatus caused an initial contracture of the ileum which was sustained for 20-25 min. In addition, the venom induced a series of shorter, more intense contractions which occurred at intervals of 2-8 min and continued after the initial contracture had declined. The height of the initial long-lasting contracture was markedly reduced by atropine, Lidoflazine and tetrodotoxin and was completely blocked by BOL-148, Melleril, Largactil, phenylbutazone, Dibenzyline and propranolol. Atropine, Dibenzyline and phenylbutazone reduced the heights of the shorter contractions elicited by the venom and these contractions were completely blocked by BOL-148, Largactil, propranolol, Lidoflazine and tetrodotoxin. C. magus venom elicited a single contracture of the ileum which was sustained for 10-17 min. The height of the contracture was reduced by Dibenzyline and atropine and was completely blocked by phenylbutazone, Lidoflazine, propranolol, tetrodotoxin and high concentrations of BOL-148. Differences in the actions of C. striatus and C. magus were detected. The action of C. striatus venom was exerted directly on the ileal musculature as well as indirectly via the ileal nerves. Experiments with antagonists indicate that the venom promotes the release of transmitter substances such as acetylcholine and 5-hydroxytryptamine from the tissues of the ileum. On the other hand, the action of C. magus venom was exerted only indirectly via nervous elements and stems from an excitatory action of the venom on ileal nerves.